Hello,
1) As you might expect, the so called god rays will be most visible to the render camera when the sun is in front of the view. That is, as in nature, the rays your probably after will be strongest when the sun is at a slightly low level relative to the forward horizon. If you hold your arms out like a cross, every thing 180 degrees from one hand to the other in front, is a place the sun will produce good rays from, depending on the the scene.
The default clouds can create this effect pretty easily. Its just a mater of placing the sun in the right place relative to the camera, and getting a good "seed" in the clouds. From there you can build up the clouds and fine tune the POV and sun position. Additionally, if you are using T3, once you get the god rays working like you want, you can add a spot light to help give that little extra bit to hit your target more directly.
One thing you may want to do is start a new scene and just play with the camera sun and some clouds. Once you get something you like you can save a clip file and import it to the scene with the terrain you made, and fine tune it even further there. The real plus to doing it this way is you will not have to wait for the terrain to render, in order to see the full scene.
Another thing you can do is search file sharing for "god rays" and download a community provided clip, and import that to play with.
Getting the rays is pretty easy, but making them look great can be a good bit of work depending on various things.
2) Yes.
Go to the "renderers" tab at the top of the UI. Go to "Advanced" in the renderer your using; Full or Quick. reduce the max thread, or the size of the "subdiv cache"... It is one or the other, maybe both... Im not sure I remember right now. The point is that is where you make the adjustment.
You want to leave only enough system resources for basic internet, maybe some music. But you should let TG have all you can spare, or you will face increasingly unnecessary render times. TG is hungry, it will eat every bit of power you give it, and you should give it as much as you have. The faster you can render the better.
3) There are a number of tuts available. I don't have the time right now to dig up links, a new series was just posted by GeekAtPlay. And there is a site called "CGscenery" too. Also a file in sharing called "a get started guide for the terrified" that has help a few thousand people.
Hope this helps. If not Im sure someone will correct anything that needs correcting.
see ya.
